Method and apparatus for completing a well in vertically spaced porous strata



United States Patent 1111 Inventor williamEshmyallef 2,303,134 11/19420196116611.... 166/228 SealBeach,Callf0rnIa 2,371,385 3 1945 Eckell66/228X 21] AppLNo. 769,494 2,401,035 5/1946 Akeyson etaL. 166/205 2Filed Oct-22, 1968 2,796,939 6/1957 Woodruff 166/228 45] Patented t-1970 3,097,693 7/1963 T6661 l66/297X [73] AssigneeUnionoilcompsnyofcahfoma 3,149,671 9/1964 Alexander 166/228X m p ifi gggg Primary Examiner- Ernest R. Purser [5 4] METHOD AND APPARATUS FORCOMPLETING A WELL IN VERTICALLY SPACED POROUS [56] References CitedUNITED STATES PATENTS 2,033,562 3/1936 Wells 166/297X 2,167,191 7/1939Vietti et al.. 166/228X 2,185,522 l/ 1940 Rollins 166/205 AssistantExaminer-lan A. Calvert Att0rr1eysMilton W. Lee, Richard C. Hartman,Lannas S.

Henderson, Dean Sandford and Robert E. Strauss ABSTRACT: A method forcompleting wells in incompetent fonnations wherein a prepacked gravelliner is cemented into place in the well adjacent to one or moreproductive zones, and thereafter the gravel pack and cement sheath isperforated to establish communication between the producing zones andthe interior of the liner The apparatus comprises an imperforate gravelpack assembly. The gravel pack can be divided into longitudinal sectionsby horizontal partitions located so as to coincide with impermeablestrata separating the producing zones. Any selected producing zone canthen be placed on production by perforating the section of gravel packand outer cement sheath adjacent to that zone, and any zone can be shutoff by plugging the adjacent section of gravel 4 pack.

Patented Oct. 20, 1970 Sheet 1 of3 gen 34 INVENTOR.

X V/Al /4/l/ 5 51901144472? gm. 4770 fr Patented Oct. 20, law

Sheet Patented Oct. $30, 1970 Sheet ovu- ...%a v n w -w v 14 44/444 5.swan/44 75/? METHOD AND APPARATUS FOR COMPLETING A WELL IN VERTICALLYSPACEI) POROUS STRATA This invention is directed to the completion of awell in an earth formation, and more particularly to the completion of awell in an incompetent earth formation composed of unconsolidated orloosely consolidated earth particles.

Recoverable fluids such as petroleum oil, gas and water are frequentlyfound in subterranean formations comprised of unconsolidated or looselyconsolidated sand and sandstone. Also, some otherwise consolidatedformations become incompetent when certain fluids are produced from orinjected into the formation. When such incompetent formations arepierced by a well and the connate fluids therein removed, the loose orweakly bound sand particles become dislodged and are entrained in thefluid. The dislodged sand is moved into flow channels causing pluggingand a reduction in permeability of the formation. Further, sand canaccumulate in the well causing plugging, and can be carried to thesurface with the withdrawn fluid. Thcsc entrained particles cause severeerosion of underground strainers and liners, the producing string,pressure control valves, pumps and flow lines. Oil produced fromincompetent formations often requires special treatment to removeentrained sand, and substantial quantities of the entrained sand can bedeposited in production tanks causing cleaning and disposal problems. Inextreme cases, sufficient sand can be removed from the producingformation to cause it to collapse under overburden pressure resulting inloss of the well. Similar problems are encountered in the injection ofwater, gas and other fluids into unconsolidated or loosely consolidatedformations, or into formations which become incompetent upon theinjection of the fluid.

Various types of strainers, screens and gravel packs have been proposedto prevent entry of incompetent sands into the well. These devices areplaced in the well adjacent to the producing zones. The produced fluidspass through one or more strainers or screens, or through a body ofgravel or other particulate matter of a size selected to prevent passageof the dislodged earth particles into the well. One conventional methodof bottom hole completion is to install a screen or slotted liner in theproducing zone and then to place gravel or other particulate matter ofselected size around the exterior of the liner to form a body of filtermaterial in the annulus between the liner and the well wall.

While these techniques have sometimes been effective in limiting theentrainment of sand into the well, other problems result from their use.First, the particulate matter used as the filtering medium generallycomprises a mixture of particles of different sizes carefully selectedto prevent passage of the entrained earth particles into the well. Therange and distribution of particle sizes used in the filter body dependsupon the size of earth particles expected to be entrained from the formation in which the well is completed. However, uniform distribution ofthe filter particles cannot be assured when the particulate matter ispumped into the annulus. Hence, some portions of the filter body undulyrestrict the flow of fluids into the well, while other portions are noteffective in preventing the entrainment of earth particles into thewell. Secondly, the gravel pack deposited in the well has vertical aswell as horizontal permeability and fluids can flow vertically throughthe annulus preventing the production of only selected zones of theproducing formation. Lastly, because of the high cost of rig time, it isdesirable to minimize the time required for completion of the well andto reduce work over and repair operations.

Accordingly, one object of the present invention is to provide a methodand apparatus for completing a well in an unconsolidated earthformation. Another object is to provide an efficient completion methodrequiring a minimum of rig time and reducing expensive work over andrepair operations. Still another object is to provide a method andapparatus for installing a filter body in a well so as to provideuniform distribution of the filter particles within the body. A furtherobject is to provide a method and apparatus for completing a well in anbetween vertically spaced producing zones. A still further object of theinvention is to provide a well completion method and apparatuspermitting any selected producing zone to be placed on production, andthe production from any selected zone to be shut off without adverselyaffecting the production from other zones. Other objects and advantagesof the invention will be apparent from the following detaileddescription.

Briefly, this invention is directed to a method for completing a well inan unconsolidated earth formation in which a prepacked gravel liner iscemented into place in a well adjacent to one or more productive zonesand the gravel pack and cement sheath perforated to establishcommunication with the producing zones, and to an imperforate gravelpack useful in the practice of the method. The gravel pack is containedin the annular space between a pair of imperforate, coaxially mountedtubular members and can be divided into longitudinal sections bytransverse partitions separating the annular space. The transversepartitions can be arranged so that when the gravel pack is placed in thewell, the longitudinal sections are adjacent to selected sections of atproducing zone. Any selected producing zone is placed on production oropened for fluid injection by perforating the tubular members of thegravel pack and the outer cement sheath at a point adjacent to theselected zone, and any zone can be shut off by plugging the gravel packadjacent thereto.

The construction of the preassembled gravel pack and the method ofplacing it in the well can best be illustrated by the followingdescription taken in conjunction with the accom panying drawings inwhich:

FIG. 1 is an elevation view of a preassembled gravel pack liner whichmay be used in carrying out the method of this invention;

FIG. 2 is a top view of the preassembled gravel pack liner;

FIG. 3 is a cross-sectional view taken generally along line 3-3 of FIG.2;

FIG. 4 is a cross-sectional view of a portion of an unconsolidatedformation showing a well completed by the method of this invention; and

FIG. 5 is a cross-sectional view of a well completed by the method ofthis invention in an earth formation comprised of a plurality ofproducing zones separated by impervious strata.

Referring now to FIGS. ii through 3, inclusive, there is shown itprcusscmbled, gravel packed liner comprised of an inner impcrioratetubular member it) which can he formed from a length of standard wellcasing of appropriate diameter and wall thickness. Tubular member 10 isprovided with threads 12 and M at either end to permit attachment ofadditional sections of preassembled liner, or well casing, byconventional threaded couplings. Alternatively, one end of tubu larmember 10 can be provided with male threads and the other end withfemale threads adapted to engage similarly threaded tubular members.Also, the threads can be omitted and tubular member 10 attached to theadjacent tubular sections by welding, or other means, if desired. Theouter shell of the ipreassembled, gravel packed liner is made up of oneor more imperforate tubular sections of larger diameter than tubularmember 10. In the illustrated embodiment, the outer shell is comprisedof three tubular sections 16, 18 and 20 having the same diameter largerthan that of inner tubular member 10 and maintained in fixed, spacedrelationship concentric with tubular member 10 by means of plates 22,24, 26 and 28 so as to form the annular chambers 30, 32, and 34 on theexterior of tubular member 10. Alternatively, the end plates 22 and 28can be replaced by welding caps cut out to receive member 10, or byother means of providing a rounded end construction. Chambers 30, 32,and 34 are filled with particles which form filter bodies capable ofpassing fluids, but which prevent the passage of sand from the formationinto the interior of tubular member 10 on its subsequent perforation.Although tubular member 10 can be constructed with any desired length,it is convenient to construct member 10 from standard sections of casinghaving a length of about 30 feet.

unconsolidated formation so as to restrict the flow of fluids Thelengths of the individual tubular members comprising the outer shell ofthe preassembled, gravel packed liner and the spacings between thetransverse plates can be adjusted to provide annular chambers havingdifferent lengths, as hereinafter more fully described.

The aforementioned preassembled, gravel packed liner can be convenientlyconstructed by attaching the bottom plate to the inner tubular member bywelding, or other convenient means, and then attaching the outer tubularmember. The annular chamber is then filled with particulate material ofselected size, and the next plate and outer tubular member installed. Apreassembled gravel packed liner having any desired number of sectionscan be constructed by this technique. In the embodiment specificallyillustrated in F165. 1 through 3, inclusive, plate 22 is welded totubular member 10 at a point near threaded end 14. Outer tubular member16 is then welded to plate 22 and the annular chamber formed by theconcentric tubular members filled with particulate material of selectedsize. Next plate 24 is welded to tubular members l-and 16 to close thechamber 30. Tubular member 18 is then welded to plate 24 to form thechamber 32, which is also filled with particulate material. This chamberis closed by welding plate 26 to tubular members and 18, and the nexttubular member is welded to plate 26. Chamber 34 is filled withparticulate material and end plate 28 welded in place.

The particulate material packed into the annular chambers must be of asize that will bridge earth particles entering through the perforationsultimately formed in the outer tubular member to prevent their passageinto inner tubular member 10, and which will bridge the perforations inmember 10 to prevent entrainment of the gravel from the annular chamber.Preferably, the size range and size distribution of the particulatematerial is selected based on the size of the earth particles expectedto be entrained from the formation. Various techniques are available fordetermining the optimum gravel size for any particular size of formationsand particles. Satisfactory bridging can be obtained when the size ofgravel particles is 10 to 13 times the 10 percentile sand grain size.

The proper size of gravel particles can be readily determinedby making aTyler screen analysis of the formation particles, plotting the resultson a cumulative weight precentage graph, determining the size offormation particle at the 10 percentile on the graph, and selecting agravel having a size 10 to 13 times this size.

In the practice of this invention, a well is drilled into a formation inconventional manner. To complete the well, a prepacked gravel liner suchas illustrated in F108. 1 through 3 is placed in the well adjacent to aproductive zone. A cement slurry is then pumped down through the innertubular member and up around the exterior of the liner. The cement fillsthe void between the exterior of the prepacked liner and the well wall,and upon hardening, forms a seal preventing fluids from flowing aroundthe exterior of the liner. After the liner is cemented in the well, agun perforator is lowered into the interior of the inner tubular memberand the liner walls and cement sheath perforated with shaped charges orprojectiles fired outwardly through the liner walls and cement sheathinto the surrounding formation. The spacing and orientation of theperforations can be varied to provide the desired producing or fluidinjection channels communicating the interior of the liner with theformation.

The method of this invention is further illustrated in FIG. 4 wherein aschematic view of a typical well completed by the method of thisinvention is shown. The well is comprised of a rather large diameterbore hole 102 drilled into earth strata 100. A first string of surfacecasing 104 is set to the bottom of bore hole 102. The surface casing isthen cemented in the bore hole by pumping cement down the interior ofthe casing and upwardly around the exterior so as to fill the annularspace between the exterior of the casing and the face of the bore hole.The cement is conventionally displaced through the casing by drillingmud, and drilling mud is displaced from the annulus by the cement. Onhardening, the cement forms a sheath 106 on the exterior of casing 104that provides an effective, impermeable seal between the formation andthe casing.

After surface casing 104 is set and cemented, a smaller diameter borehole is drilled through the casing. Drilling is continued until thesubsurface conditions require the setting of an intermediate casingstring, such as casing 112. lnter mediate casing 112 is set and cementedin place by pumping cement down the interior of the casing and upwardlyaround the exterior so as to fill the annular space between the exteriorof the casing and the formation face. Cement sheath 114 affords afluid-tight seal between the casing and the formation face. If desired,sufficient cement can be pumped into the annulus to wholly or partlyfill the annulus between intermediate casing 112 and surface casing 104.

The well is completed in the production zone by drilling a smallerdiameter bore hole into oil or gas-bearing strata 122. Production casing124 having a prepacked gravel liner 126, such as hereinbefore described,attached to its lower end is set in the casing and cemented in place. Asbefore, cement is pumped down casing 124, through the interior tubularmember of liner 126, and upwardly around the exterior of liner 126. Itis essential that the liner walls are imperforate to avoid entrance ofcement into the gravel pack during the cementing operation. Asillustrated, production liner 124 can be cemented to the surface, thusproviding an impermeable sheath 128 to seal between the exterior ofliner 126 and the formation face and in the annular space betweenproduction casing 124 and intermediate casing 112. Alternatively, onlythat portion of the annulus surrounding liner 126 need be cemented tofacilitate completion of the well by the method of this invention.

After the cementing operation has been completed, the liner isperforated by positioning a carrier containing one or more perforationguns loaded with shaped charges or projectiles in the interior of theliner and detonating the charges in conventional manner. The spacing andorientation of the perforations are controlled by the position of thegun in the carrier, and by the position of the carrier in the liner. Theprojectile or shaped charge must be of sufficient strength to perforatethe inner tubular member of the liner, pass through the body of gravelbetween the tubular members, perforate the outer tubular member and thesurrounding cement sheath, and preferably penetrate into the formationadjacent to the well. The perforations in the tubular members should besufficiently small to prevent entrainment of the particulate filtermaterial from the annular chamber. Preferably, the diameter of theperforations is no larger than 3 times the diameter of the gravelparticles. In the well completion illustrated in FIG. 4, the liner, thesurrounding cement sheath, and the formation are perforated at 130, 132and 134.

The use of the method of this invention in completing a well in amultistructured formation is illustrated in FIG. 5. In the lilustratedembodiment, bore hole 200 is drilled through relatively impermeableshale strata 202, 206, 210, 214, 218, 222, and intermediate porousoil-bearing strata 204, 208, 212, 216, 220 and 224, and is terminated inunderlying impervious strata 226. Prepacked gravel liners 230, 232 and234 are assembled on production casing 236 by means of threadedcouplings 238, 240 and 242. Liner 230 is constructed with two transversehorizontal baffles 244 and 246 located so that they are adjacentimpervious strata 222 and 218, respectively, when the liner assembly ispositioned in the bore hole. Liners 232 and 234 are constructed withtransverse horizontal baffles 248 and 250 located so that they areadjacent to impervious shale strata 210 and 206, respectively, when theassembly is positioned in the bore hole.

The liner assembly is run into the bore hole and positioned so that thebaffles are aligned with the proper impervious strata. Cement is pumpeddownwardly through the casing 236 and through the liner assembly. Thecement is displaced from the interior conduit upwardly around theexterior of the liners and around casing 236. The casing can be cementedto the surface, if desired. On hardening, the cement forms animpermeable sheath 252 filling the annular space between the exterior ofthe liners and the formation face providing lateral support for theliners and sealing against the flow of fluids.

After the cement has hardened sufficiently, the liners and surroundingcement sheath are perforated to establish communication between theproduction casing and the producing strata. Liner 230 is perforatedat260, 262, 264 and 266 so as to open permeable strata 216 and 224 toproduction. As previously stated, the number and pattern of theperforations can be varied as desired. In the illustrated embodiment,the center section of liner 230 is not perforated. Thus, stratum 220 isnot opened to production. However, this can be opened for production orfluid injection at any future time by perforating the liner and cementsheath as hereinabove described. Liner 232 is perforated at 268, 270,272, 274, 276 and 278 so as to open strata 2% and 217; for production.Similarly, liner 234 is perforated at 280, 282 and 284 to open stratum204. The perforations are made by firing shaped charges or projectilesthrough the inner tubular member of the liner, the gravel pack, theouter tubular member, the cement sheath, and into the adjacentformation.

Thus, it is apparent that production from various zones of amultistructures formation can be controlled by perforating only thosesections of well liner adjacent to the selected zone, and by controllingthe number and location of perforations in any particular section ofliner. Further, production or fluid injection into any selected zone canbe discontinued without adversely affecting other zones by injectingcement, resin, or other plugging material into the section of lineradjacent to the selected zone, thereby rendering that section of filterbody impermeable to fluid flow.

The well completion method and apparatus of this invention can beemployed in completing production wells, such as those normally used inrecovering oil, gas, or water from earth formations, and in completinginjection wells, such as those used for injecting water and other fluidsinto an earth formation in secondary and tertiary oil recoveryoperations.

While particular embodiments of the invention have been described, itwill be understood, of course, that the invention is not limited theretosince many modifications can be made and it is intended to includewithin the invention any such modifications as fall within the scope ofthe claims.

lclaim:

ll. A prepaclted liner for completing a well in an earth formation,which comprises:

a first elongated imperforate tubular member;

an outer imperforate cylindrical shell comprised of a plurality ofsecond tubular members having the same diameter larger than that of saidfirst tubular member, said second tubular members being mounted end toend coaxially with said first tubular member;

transverse members attached to said first tubular member and to saidsecond tubular members intermediate adjacent of said second tubularmembers;

means at the outer ends of said second tubular members to close theannular opening between said first and second tubular members; and

a body of particulate filter material contained within the annulusbetween said first and said second tubular memhere.

2. A method for completing a well in an earth formation comprised of aplurality of vertically spaced porous strata, which comprises:

placing an imperforate tubular prepacked liner having a plurality oflongitudinally disposed, closed annular filter beds in a bore holepenetrating said earth formation so that said filter beds are positionedadjacent said porous strata;

cementing said liner in said bore hole to provide a substantiallyfluid-tight sheath of cement in the annulus between said liner and theformation wall; and

perforating, said liner and said cement sheath adjacent selected of"said struts to establish communication between the interior of saidliner and said selected strata through the filter beds adjacent saidselected strata, at least one of the filter beds in said liner remainingclosed.

3. The method defined in claim 2 wherein the cement is pumped into theannulus in the form of a slurry and permitted to harden prior toperforation.

4. The method defined in claim 2 wherein said liner is perforated byfiring a projectile from the interior of said liner through said linerand said cement sheath.

5. The methoddefined in claim 2 wherein said liner is perforated bypassing a high energy jet through said liner and said cement sheath.

6. The method defined in claim 2 wherein communication between at leastone of said porous strata and the interior of said liner is interruptedby placing a plugging material in the annular filter bed adjacent tosaid selected strata.

'7. The method defined in claim 6 wherein said liner and said cementsheath adjacent at least one of the previously closed filter beds aresubsequently perforated to establish communication between the porousstrata and the interior of said liner.

8. The method defined in claim 2 wherein formation fluid is producedthrough the filter beds adjacent the selected strata, and wherein saidliner and said cement sheath adjacent at least one of the previouslyclosed filter beds are subsequently perforated to establishcommunication between the porous strata and the interior of said liner.

9. The method defined in claim 2 wherein a plurality of axiallyconnected imperforate prepacked liners are inserted into said bore hole.

10. The method defined in claim 2 wherein each of said filter bedscomprise a body of particulate filter material.

Ill. The method defined in claim it) wherein said filter material isgravel of a selected size range.

112. A method for completing a well in an earth formation comprised of aplurality of vertically spaced porous strata penetrated by a bore hole,which comprises:

determining the strata spacing by measuring the depth and verticalthickness of said porous strata;

assembling an imperforate tubular prepacked liner having a plurality oflongitudinally disposed, closed annular filter beds axially positionedon said liner so that the spacing of said filter beds corresponds tosaid strata spacing; placing said prepacked liner in said bore hole sothat said filter beds are positioned adjacent said porous strata;

cementing said liner in said bore hole to provide a substantiallyfluid-tight sheath of cement in the annulus between said liner and theformation wall; and

perforating said liner and said cement sheath adjacent selected of saidstrata to establish communication between the interior of said liner andsaid selected strata through the filter bed adjacent said selectedstrata. 13. A method for completing a well in a formation comprised of aplurality of vertically spaced porous strata, which comprises:

placing an imperforate tubular prepacked liner having a plurality oflongitudinally disposed, closed annular filter beds in a bore holepenetrating said earth formation so that said filter beds are positionedadjacent said porous strata; cementing said liner in said bore hole toprovide a substantially fluid-tight sheath of cement in the annulusbetween the exterior of said liner and the formation wall;

perforating said liner and said cement sheath adjacent selected of saidstrata to establish communication between the interior of said liner andsaid selected strata through the filter beds adjacent said selectedstrata; and

treating at least one of the filter beds adjacent the selected stratawith a plugging material so as to render the treated filter bedssubstantially impermeable to fluid flow.

14. A prepaclted liner for completing a well in an earth formation,which comprises:

an elongated imperforutc tubular member;

an outer imperfoiate cylindrical shell having a diameter greater thanthat of said tubular member, said cylindrical shell being mountedcoaxially with said tubular member;

transverse members radially attached to said tubular member and to saidcylindrical shell at the top and bottom of said cylindrical shell and atspaced intervals therebetween so as to define a series of longitudinallydisposed closed annular chambers; and

a body of particulate filter material contained within each of saidclosed chambers.

15. A prepacked liner for completing a well in an earth formation, whichcomprises:

a first elongated, imperforate tubular member;

a plurality of imperforate second tubular members having a commondiameter greater than that of said first tubular member and mountedcoaxially on said first tubular member;

transverse members at the ends of said second tubular members radiallyattached to said first tubular member and to said second tubularmembers; and a body of particulate filter material contained within eachof the annuli between said first and said second tubular members. 16.The apparatus defined in claim 15 wherein said filter material iscomprised of gravel of a selected size range.

17. The apparatus defined in claim 15 including means for attaching saidliner to a tubular casing string.

18. The apparatus defined in claim 15 wherein said second tubularmembers are mounted abutting each other on said first tubular member.

